This proposal is designed to continue the Seattle Longitudinal Study, a major longitudinal-sequential inquiry into the development of intellectual abilities over the adult life span. The present study seeks to implement a fifth (year 28) data collection which will involve the retesting of approximately 700 survivors from the first four waves, and the initial testing of a fifth wave of approximately 650 persons all within the age range from 22 to 98 years of age. All participants are members of a health maintenance organization in the Pacific Northwest. Prior data are available on 2,810 persons on Verbal Meaning, Spatial Orientation, Reasoning, Number, Word Fluency, Flexibility-Rigidity, and other personality scales. More limited data are available on measures of perceptual speed, life styles, and health histories. The psychometric battery will be enlarged for the present cycle to permit structural analyses. Further extensions to limited component analyses (angles of spatial rotation and strategies in solving inductive reasoning problems), the inclusion of ecological validity measures and measures of perceptual speed and verbal memory will broaden the scope of the longitudinal study. Principal questions to be addressed continue to include: 1. Does intelligence change across age differentially by ability? 2. What are the age levels at which reliable age decrement can be detected, and what is the magnitude of such decrement? 3. What are the patterns of generational differences in abilities and what are their magnitude? And, 4. What accounts for individual differences in intraindividual change across adulthood.